WO2000031316A1

WO2000031316A1 - Co-Ti ALLOY SPUTTERING TARGET AND MANUFACTURING METHOD THEREOF

Info

Publication number: WO2000031316A1
Application number: PCT/JP1999/003479
Authority: WO
Inventors: Kazushige Takahashi; Hirohito Miyashita
Original assignee: Japan Energy Corporation
Priority date: 1998-11-20
Filing date: 1999-06-29
Publication date: 2000-06-02
Also published as: KR20010034218A; EP1091015A4; TW475946B; EP1091015A1

Abstract

A method of manufacturing a Co-Ti alloy sputtering target containing not more than 100 ppm of oxygen and having a grain size of not larger than 50 νm, comprising forming a Co-Ti alloy ingot by vacuum-melting and casting a Co-Ti alloy containing 0.5 to 20 wt.% of Ti, and then hot-working the ingot. The Co-Ti alloy sputtering target containing the above small amount oxygen is useful for forming a sputtering thin film which is excellent in film-forming uniformity and has few particles.

Description

Specification

Technical field of Co—Ti alloy sputtering target

The present invention relates to a Co-based alloy sputtering target which has a low oxygen content, has good film forming uniformity (uniformity), and can provide a low-particle sputtered thin film.

Background art

As a method of forming a semiconductor thin film, a sputtering method is widely used. In the sputtering method, a substrate serving as an anode is opposed to a target serving as a cathode, and an electric field is generated by applying a high voltage between the substrate and the target under an inert gas atmosphere. At this time, the ionized electrons collide with the inert gas to form plasma, and the cations in the plasma collide with the target surface and strike out the constituent atoms of the target. This is based on the principle that a film is formed by adhesion.

At present, most of the commonly used sputtering uses a method called so-called magnetron sputtering. The magnetron sputtering method is a method in which a magnet is set on the back side of a target and a sputtering is performed by generating a magnetic field in the direction perpendicular to the electric field on the surface of the getter. It has the features of being able to stabilize and increase the density and to increase the sputtering rate.

In general, a thin film is formed on a substrate by using such a magnetron sputtering method.

Conventionally, a Co-Ti alloy sputtering thin film requires strict control of the Ti content, and it has been necessary to form a uniform film on a wafer.

As one method of forming such a Co—Ti alloy sputtering thin film, first, two types of targets, a Co target and a Ti target, are prepared, and these are alternately sputtered on a substrate to a predetermined thickness. After film formation, heat treatment An o-Ti alloy thin film has been used. However, this involves a number of steps of forming a thin film, which complicates the control of the film thickness and the like, and has the disadvantage that it is costly and impractical.

Therefore, as an alternative to the above, it was conceivable to use a so-called mosaic target in which Co plates and Ti were alternately arranged in a plane and placed E. This is efficient because the sputtering target does not need to exchange the two types of targets, the Co target and the Ti target, each time. The composition of the i-alloy tends to be non-uniform on the wafer, which also has the disadvantage of poor quality and impractical.

Due to the above-mentioned disadvantages, a sintered product target, which is often used for high melting point metal targets such as silicide and W and Mo, was used.

However, there were some problems in the manufacturing process of this sintered compact target. This means that it is difficult to obtain high-purity Co powder raw materials suitable for semiconductor devices, which requires a special manufacturing process to obtain the powder, and is extremely expensive. In addition, the sintered body target has a problem that the oxygen content is high and the resistance of the C 0 — Ti alloy thin film is increased.

No matter how the manufacturing conditions are improved, the sintered target cannot have a density of 100%, and as a result, the low density of the sintered target has been one of the causes of particle generation .

Furthermore, it is said that the discharge does not occur unless the Ar gas is increased during sputtering film formation, which makes the discharge unstable, that the deposition rate (film formation rate) fluctuates greatly, and that it is very difficult to control the magnetic permeability. There were drawbacks.

As described above, the range of the film forming conditions for obtaining the desired characteristics was extremely narrow, and a satisfactory Co—Ti alloy target could not be obtained.

According to the present invention, a Co—Ti alloy target is produced by a melting method, the amount of oxygen is reduced, the production process of the target and the film formation process are shortened, and a good thin film with uniformity can be obtained. The present invention relates to a Co—Ti alloy sputtering target and a method for producing the same. Disclosure of the invention

In order to solve the above-mentioned problems, the present inventors can improve the uniformity of film formation and reduce the amount of oxygen by manufacturing a Co—Ti alloy sputtering target by a vacuum melting method. It was found that thin films with good reproducibility and high quality could be obtained under stable manufacturing conditions.

The present invention is based on this finding,

A Co—Ti alloy sputtering target containing 1 Ti 0.5 to 20 at% and manufactured by a vacuum melting method.

(2) The sputtering target as described in (1) above, wherein the oxygen content is 100 ppm or less.

(3) The sputtering target as described in (1) or (2) above, wherein the crystal grain size is 50 / m or less.

(4) The sputtering target according to (1) to (3) above, wherein the maximum magnetic permeability in the in-plane direction of the target is less than 30, and the maximum magnetic permeability in the thickness direction is 5 or more and less than 100.

After forming a Co-Ti alloy ingot by vacuum melting and forming a Co-Ti alloy containing 5 Ti 0.5 to 20 at%, the ingot is formed into a target by hot working. For producing a Co—Ti alloy sputtering target

, Are provided. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic explanatory view showing a composition analysis position on a wafer. Embodiment of the Invention

The Co—Ti alloy sputtering target of the present invention contains Ti 0.5 to 20 at%. The balance is basically Co and may contain acceptable unavoidable impurities. In manufacturing the target, first, high-purity Co and Ti are dissolved in a vacuum. Although high-purity Co is used as a raw material for Co, its purity is commercially available 9 9. More than 9% can be used. Use Ti with a purity of 99.955% or more.

After smelting this Co-Ti alloy, it is made into a predetermined block (ingot), hot forged or rolled, and then finished to form a flat plate or other target shape that can be set in a magnetron sputtering device. I do.

The above hot working is 800-1190. Perform in the range of C. This hot working is effective as a means for making a relatively coarse structure as it is and making it finer and for refining crystal grains.

By this hot working, the quality of the target of the present invention can be further improved.

The alloy target of the present invention obtained as described above has an oxygen content of 100 ppm or less and a crystal grain size of 50 / ΛΠΙ or less.

Further, the oxygen content of the Co—Ti alloy sputtering target of the present invention can be set to 80 ppm or less, and the crystal grain size can be set to 30 or less.

The reason for setting the Ti content of the Co—Ti alloy sputtering target of the present invention to 0.5 to 20 at% is that if the Ti content exceeds 20 at%, the flatness of the sputtering film becomes poor. This is because the specific resistance increases, and if it is less than 0.5 at%, the effect of containing Ti is lost.

Further, in the present invention, a target having an oxygen content of 1 OOP pm or less can be easily obtained. However, if the oxygen content exceeds 1 OOp pm, the resistance of the Co—Ti alloy thin film increases, so the upper limit is set. It is necessary to be within this range. Preferably, as described above, the content is 80 ppm or less.

When a sputtered film is formed by using the in-situ Co—Ti alloy target of the present invention, which has a dense structure with a crystal grain size of 50 im or less, Co with much better uniformity than the conventional sintered compact target is obtained. — Ti alloy thin film can be formed on a substrate (wafer).

The reason for performing the hot working in the range of 800 to 1190 ° C is to eliminate Ti segregation at the ingot stage and perform hot working without causing cracks.

The Co—Ti alloy sputtering target of the present invention has a maximum magnetic permeability in the in-plane direction.

Four

Corrected ^ paper (Rule S1) The permeability is less than 30, and the maximum permeability in the thickness direction is 5 or more and less than 100.

When sputtering is performed using a Co—Ti alloy target having a low magnetic permeability by this smelting method, the discharge is stable, and a thin film having few defects such as particles can be obtained.

In addition, since the variation of the Ti concentration in the Co—Ti alloy target of the present invention becomes ± 0.2 wt% or less, a stable thin film with good reproducibility can be obtained. Since the oxygen content of the thin film obtained by sputtering can be set to 100 ppm or less and further to 80 ppm or less similarly to the target, a low-resistance film can be formed. Further, the thin film itself has a uniform thickness, has no component segregation, has a dense structure, and can be obtained as a thin film excellent in uniformity. Examples and comparative examples

Hereinafter, description will be made based on examples and comparative examples. This embodiment is merely an example, and the present invention is not limited to this embodiment. That is, the present invention is limited only by the scope of the patent claims, and encompasses various modifications other than the examples included in the present invention.

(Example 1)

Co-Ti alloy was vacuum-melted using a vacuum induction melting furnace, using Co with a purity of 99.99% or more and Ti with a purity of 99.955% or more. The dissolved products are Co-10at% Ti and Co-15at% Ti.

Table 1 shows the composition of these alloys. After melting and manufacturing of the Co—Ti alloy, the obtained ingot (170 × 200 × 301;) is soaked (held at 1100 ° C. for 2 hours). Hot rolled in a pass.

Samples were cut out from these hot-rolled sheets and subjected to oxygen content analysis, magnetic property measurement and microscopic structure observation. The amount of oxygen was analyzed using an oxygen analyzer of LE CO. Magnetic properties were measured with a B-H meter using a 4πI coil at a maximum magnetic field of 1000 Oe. The microstructure was observed using an optical microscope after the cross section was polished and further etched.

Table 2 shows the results of the oxygen content analysis. As shown in Table 2, two types of C 0 — T i The oxygen content of the alloy was 75 ppm, and the result was that the oxygen content was lower than that of the sintered product of the comparative example described later. In the measurement results of the magnetic properties, the maximum magnetic permeability in the in-plane direction was less than 30 and the maximum magnetic permeability in the thickness direction was 5 or more and less than 100, and a low magnetic permeability Co—Ti alloy was obtained. Furthermore, according to the observation with an optical microscope, it had a dense structure without cracks or component segregation.

Composition Remarks

Co—10 a t% T i dissolved product

An example

Co 5 at% T i Melt ratio

Comparative Co-10at% T sintered product

An example

Co—15 at% Ti sintered product

Table 2

(Comparative Example 1)

Co powder having a purity of 99.99% or more and Ti powder having a purity of 99.995% or more were used as raw materials and sintered at 1150 ° C. in vacuum using a hot press apparatus. There are two types of sintered products: Co-10at% Ti and Co-5at% Ti. As in Example 1, Table 1 shows the composition of these alloys.

Samples were cut out from these sintered products, and subjected to oxygen content analysis, magnetic property measurement, and microscopic observation using the same measuring device as in Example 1.

The results of the oxygen content analysis are shown in Table 2 same as in Example 1. As shown in Table 2, the oxygen content of the two Co-Ti sintered products of Comparative Example 1 was 36 Oppm and 37 Oppm, respectively, and the oxygen content increased compared to the melt-rolled product of Example 1 and was poor. The result was.

According to the observation with an optical microscope, a coarse structure peculiar to the sintered product is obtained, and a dense tissue is not obtained as compared with the melted product. Also, in the measurement results of the magnetic properties, the magnetic permeability is high, which is inferior to the examples. Next, in order to investigate the amount of particles generated by sputtering and the variation in the composition of the components in the thin film, a comparison was made with the two types of rolled sheets of Co-10at% Ti and Co-15at% Ti alloys in Example 1 above. From the sintered plates of two types of Co-10at% Ti and Co-15at% Ti of Example 1, an evening get of φ3 mm was prepared.

(Comparative Example 2)

In addition, a mosaic target was prepared to compare the integrated rolled plate target with the sintered plate target. The Co and Ti of this mosaic target were obtained by melting and rolling under the same conditions as in Example 1 individually with the same purity as in Example 1. Then, a Ti chip (3 mm square) was placed on a Co target so that the rolled sheet obtained in this manner had the same area ratio of the sputtered surface as in Example 1, and the same size ( Φ3〃) mosaic target.

Using the target prepared above, a thin film was formed on a silicon wafer by using a sputtering apparatus, and the generation state of particles of> 0.3 zm and fluctuation of the composition in the thin film were examined. The particle generation was analyzed quantitatively using a particle counter, and the composition of the components in the thin film was analyzed using EPMA.

The sputtering conditions were as follows: distance between substrates: 60 mm, gas pressure (Ar): 0.5 Pa, and voltage: 500 V.

Table 3 shows the particle measurement results. As is clear from Table 3, the amount of particles generated in the target prepared by the melt rolling in Example 1 was 0 Zcm ² and 0.02 particles / cm ² , which were extremely small.

On the other hand, the sintered compact target of Comparative Example 1 showed a bad result because the amount of generated particles was more than one digit.

The amount of particles generated by the mosaic target manufactured from the melt-rolled product of Comparative Example 2 was better than that of the sintered compact target of Comparative Example 1, but the integrated melt-rolled target of Example 1 was used. The result was slightly worse than. Table 3

Next, Table 4 shows the measurement results of the variation in the composition (T i) of the thin film formed on the silicon wafer. Figure 1 shows the measurement points of the thin film formed on the silicon wafer. Table 4 shows the analysis values corresponding to the measurement points in Fig. 1. As is clear from Table 4, the amount of variation in the composition (T i) is small for the integrated melting and rolling target of Example 1 and the sintered target of Comparative Example 1. However, mossy targets have poor compositional fluctuations on the wafer and are poor.

Since the mosaic target has a small amount of particles generated and the manufacturing process is simple, Although it appears to have advantages, it is unsuitable because of such compositional variations. In view of the above, it was found that an integrated target (Example 1) produced by melting and rolling, which generates a small amount of particles and has a small variation in the composition of the thin film formed on the wafer, is the best target. Was.

Table 4

0 The invention's effect

The Co—Ti alloy sputtering target of the present invention has a Ti content of 0.5 to 20 at%, an ingot of the same alloy by melting and ingot, and the ingot is hot-worked to have a crystal grain size of 50 m. Below, the oxygen content was reduced to less than 100 ppm.

The Co—Ti alloy target manufactured in this manner can have a Ti concentration variation within 0.2 wt%, and has a low magnetic permeability, low resistance, and a sputtered thin film with few particles on the wafer. Can be formed.

Further, it is easy to control the magnetic permeability, and there is no problem that discharge does not occur unless the Ar gas pressure is increased during film formation as seen in a sintered body target.

As a result, the discharge is stable, the fluctuation of the deposition rate is small, the range of the deposition conditions for the Co-Ti alloy thin film can be widened, and stable deposition with good reproducibility is possible. However, it has excellent characteristics as compared with the conventional mosaic target or sintered target, and has a remarkable effect that the cost can be reduced.

Claims

The scope of the claims

1. A Co—Ti alloy sputtering target containing 0.5 to 20 at% of Ding 1 and produced by vacuum melting.

2. The sputtering target according to claim 1, wherein the oxygen content is 100 ppm or less.

3. The sputtering target according to claim 1, wherein a crystal grain size is 50 zm or less.

4. The sputtering method according to claim 1, wherein the maximum magnetic permeability in the in-plane direction of the target is less than 30 and the maximum magnetic permeability in the thickness direction is 5 or more and less than 100. Get.

5. After forming a Co-Ti alloy ingot containing Ti 0.5 to 20 at% by vacuum melting and forming, the ingot is made a target by hot working. A method for producing a Co-Ti alloy sputtering gate.

Two